Cone and Fertile Stem of Equisetum . 247 
I have not considered the mesh thus closed as of a higher order than those 
closed at or just below the node. There seems little reason to doubt that 
this mode of closure of a parenchymatous mesh is secondary and due to 
poor development of xylem at the node. The amount of xylem at this level 
being insufficient to close the meshes this closure is effected slightly higher 
up by the oblique course and fusion of adjacent strands or their branches. 
It is not unlikely that, as occasionally in cones of E. giganteum , so also 
in those of E. arvense , E. hyemale , and E. palustre , the closure of meshes in 
cones with relatively wide steles and little axial xylem may sometimes be 
effected by the oblique course of the tracheides, especially where the origin 
of a mesh causes the branching of an isolated trace-bearing strand ; but this 
form of closure is not characteristic of these species. As such a mode of 
closure of meshes does not imply an increase in the amount of xylem 
locally present, the cones of E. maximum and E. limosum , in which it is of 
widespread occurrence, have relatively even more reduced vascular systems 
compared with E. arvense than is indicated in the table of statistics on 
p. 236 of my second paper on Equisetum (Browne ( 2 ). Naturally, too, 
the tracheides running obliquely — some of them transversely — across 
a mesh occupy a wider space in the longitudinal reconstruction than would 
an equal number of tracheides, the long axes of which were vertically 
directed. 
Relatively to the number of sporangiophores there are many fewer 
parenchymatous meshes in the cones of E. hyemale and E. giganteum than 
in those of E. arvense . If the small number of cases examined is repre- 
sentative, the average proportion of meshes to sporangiophores is, in 
E. arvense , rather more than twice as great as in E. hyemale , and rather 
more than three times as great as in E. giganteum. Indeed, judged by 
this standard alone, the cones of the last-mentioned species would have the 
most reduced vascular systems of any, the anatomy of which is known to us, 
the proportion of meshes to sporangiophores being very slightly lower than 
in the cones of E. maximum and E. limosum . Such a conclusion would, 
however, be erroneous. In most of its characters the cone of E. giganteum 
shows that it possesses a relatively more developed vascular system than 
the cones of E. palustre , E. maximum , and E. limosum. For example, the 
proportion of meshes closed by additional development of tracheides at the 
node rather than by their oblique course is very much greater in E. gigan- 
teum than in E. maximum or E. limosum. Then again, the proportion 
borne by the meshes of the first and second orders to the total number of 
meshes, though rather lower in E. giganteum than in E. arvense, is much 
higher than in E. palustre, E. maximum , or E. limosum. In two respects 
the cone of E. giganteum affords an example of relatively greater develop- 
ment of the xylem than even that of E. arvense. Firstly, as already 
mentioned (p. 240), the xylem tends to attain a greater radial depth than in 
